Cerebral infarction is a serious medical problem in the USA. The events which occur in the acute stage of this disease require further investigation if an effective therapy is to be developed. This study utilizes a new imaging modality, proton magnetic resonance (MR) to investigate: A. Patients 1 and 7 - 10 days after cerebral infarction and B. cats 2-8 hours and 3 and 7 days after surgically induced occlusion of the middle cerebral artery. Previous work done at the Baylor MR lab allows quantitative in vivo measurement of T1, T2, and SD in cerebral tissue. In addition, 31P spectra will be obtained in the cat brain. These MR parameters will provide new information on the state of acutely infarcted cerebral tissue. The project compares this data with: (A) morphologic changes documented by CT in patients and histology in cats and (B) blood flow documented by IMP SPECT scans in patients and 123 IMP autoradiography in cats. The project will further expand the information available from MR by developing techniques to assess cerebral blood flow. These will be evaluated by comparing the patient and cat data to the flow information available form the IMP studies. The usefullness of MR in determining the response to therapy will be evaluated in the cat stroke model by comparing the controlled infarctions in cats with the cats treated with one of several opiate anatogonists.